1. Field of the Invention
This invention relates to gas lasers having a sealed plasma chamber using either pure or mixed atomic or molecular gases. More particularly, it relates to such lasers in which the sealed plasma chamber and certain associated high voltage components and circuitry may be replaced by another of the same class by relatively unskilled personnel without a need for optically realigning the system to obtain oscillation.
2. Brief Description of the Prior Art
In general, gas lasers are constructed with a plasma chamber containing a selected gas or mixture of gases, and a set of electrodes that produce a high-intensity current that excites the atoms or molecules to high energy states. A pair of optical mirrors, which may be within or external to the plasma chamber envelope, are provided to produce regeneration, hence causing laser oscillation. The mirrors, which form the resonator for the gas laser, must be aligned accurately to cause optical regeneration.
Such gas lasers have been used in many different configurations using various atomic and molecular gases. The output spectra that are available cover a wide electromagnetic spectrum extending from the far infrared into the visible and near ultraviolet and have power capabilities from a few milliwatts to the megawatt region.
The practical applications of such lasers have been limited by a number of factors. Many kinds of lasers are effectively limited to laboratory usage because they cannot be operated in a sealed off condition without an auxiliary pumping system that either intermittently or continuously replenishes the gaseous medium. In molecular gas lasers, the composition of the gaseous medium gradually changes under operating conditions caused by molecular disassociation, giving rise to the requirement for the introduction of fresh gases into the envelope as used gases are removed. The life of a laser having a sealed envelope may also be limited by gaseous reactions or decomposition within the plasma chamber, the laser amplifying medium, that deteriorates the optical quality of the windows. For the most part, only inert gas lasers, such as helium-neon, and argon, krypton and other inert gas ion lasers have been practical for operation over an extended period of time as sealed-off units.
The expense associated with the use of many lasers is a critical factor in commercial applications. For example, there are helium-neon lasers which can be manufactured at relatively low cost and which are capable of operation under sealed conditions for a relatively long period of time. When the plasma chamber in such a laser finally fails, it may be more practical and economical to discard the entire unit rather than to replace the plasma chamber and realign the optical resonator to obtain oscillation.
In certain higher power and more expensive sealed inert gas lasers, the costs of the plasma chamber and the auxiliary equipment are high. When failure occurs in these more expensive laser systems, the plasma chamber is usually replaced, but that replacement requires skilled personnel because of the high voltages involved and the need for precise optical realignment. Nevertheless, such sealed inert-gas lasers are used commercially because the operating life is sufficiently long to justify the cost of replacement of the plasma chamber.
That is not true of molecular and most other gas lasers which have a more limited life under sealed operating conditions. For example, in lasers using carbon dioxide, excitation of the plasma causes disassociation of the gas molecules into carbon monoxide and oxygen. Such lasers are provided with a pumping station and the necessary auxiliary equipment to allow operation with a continuous gas flow. Recent developments in the use of catalysts to regenerate the carbon dioxide have lengthened the life of such sealed lasers, but most commercial units still require a flow of make-up gas to achieve acceptable operating life.
Similar and more serious problems arise with gas lasers using halides, for such gases are corrosive and surface reactions reduce the effectiveness of the optical windows. The resulting short life requires that these lasers also be provided with continuing gas replenishment and, in addition, means must be provided for collecting the corrosive used gases.
The commercial application of many kinds of prior art lasers requiring replenishment of the used gas in the plasma chamber generally require a bulky gas handling system.
The capability of quick and easy replacement of the plasma chamber and its associated high voltage components without the need for skilled personnel is an important commercial advantage that was not available prior to this invention.
Replaceable plasma chambers are known, but generally suffer from the difficulty of the requirement for optical realignment when the plasms chamber is replaced. U.S. Pat. No. 4,342,114 to Luck describes a laser in which the mirrors are formed as an integral part of the plasma chamber and the entire unit arranged so that it can be replaced. However, this arrangement, while eliminating the need for optical realignment at the time of installation, does not permit replacing the high-voltage components as an integral unit with the plasma chamber and also requires the replacement of the amplifier mirrors because they are an integral part of the plasma chamber. However, mirrors have a long life and do not need replacement, whereas the high voltage components, including the high voltage switch, typically have a shorter life and are desirably replaced along with the plasma chamber.